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Rill erosion is a serious concern in the hilly region of China with purple soil, and maize is extensively cultivated in this region. Evaluations of the dynamic mechanisms of rill erosion in sloping farmland areas are particularly important during the maize growing season to determine whether rill erosion can occur. A new ridge tillage (RT) system was designed using local agricultural methods in China. Twelve artificial rainfall experiments were conducted in three 1 × 2 m experimental plots with a slope of 15°, which is a typical slope in the study area. The rainfall intensities were designated as 1.0, 1.5, and 2.0 mm min−1. The rainfall experiments were performed in the field to determine the characteristics of run‐off and sediment transport related to rill erosion processes during different stages of maize growth and to analyse how hydraulic parameters and the sediment yield of the rill erosion process are related. The results showed that rill flow patterns were mainly classified as subcritical transition flow during all the growth stages of maize. The effects of hydrodynamic parameters on the sediment yield were ordered as follows: Reynolds number > stream power > Froude number > shear stress. The total sediment yield varied by stage as follows: seedling stage > jointing stage > mature stage > tasseling stage. The sediment yield and run‐off rate exhibited a linear relationship that was well described at the hillslope scale. To initiate soil loss in sloping farmland areas with purple soil during the maize growing season, the critical hydrodynamic shear stress and stream power must be at least 46.505 Pa and 1.541 N m−1 s−1, respectively. [ABSTRACT FROM AUTHOR]

Interactions between heavy metals in soil could affect soil heavy metal availability and plant uptake. Thus, in this study, Cd and Pb accumulation as well as plant growth of the mining ecotype (ME) and non-mining ecotype (NME) of Athyrium wardii (Hook.) in response to the exposure of Cd and Pb was investigated by a pot experiment. Although the exposure of Cd in combination with Pb further inhibited the growth of the two ecotypes in comparison with the exposure of single Cd or Pb, the ME presented lower biomass decline for the whole plant (22.0%-70.0%) than the NME among most treatments. The presence of Pb promoted Cd accumulation both in above-ground and under-ground parts of the ME. Cd concentrations in under-ground parts of the ME decreased when exposed to higher concentrations of Pb (> 600 mg kg−1). Meanwhile, the presence of Cd inhibited Pb accumulation in above-ground parts of the ME and promoted Pb accumulation in under-ground parts of the ME. Pb concentrations in under-ground parts of the ME decreased when soil Cd concentrations were more than 25 mg kg−1. The partial correlation analysis further demonstrated that the interactions between Cd and Pb stimulated Cd accumulation both in above-ground and under-ground parts of the ME and Pb accumulation in under-ground parts of the ME, while inhibited Pb accumulation in above-ground parts of the ME, showing great benefit for Pb phytostabilization by the ME. Among treatments, the bioaccumulation coefficients for Cd and Pb of the ME, varying from 2.71-31.05 and 20.09-78.06, were much higher than those of the NME. The translocation factors for Cd and Pb of the ME, varying from 0.26-0.52 and 0.01-0.10, were lower than those of the NME. These results indicate that the ME presented greater potential for the phytostabilization of soil contamination with Cd and Pb, especially for Pb. [ABSTRACT FROM AUTHOR]

Research on the variations of organic carbon (C) and total nitrogen (N) in soil aggregate fractions is important for better understanding C and N dynamics in agricultural soils. However, the effect of continuous planting of tea ( Camellia sinensis L.) after the conversion of abandoned land to tea plantation on C and N dynamics has not been studied in detail. This study aimed to investigate the shifts in C and N concentrations in soil aggregate fractions after the conversion of abandoned land into tea plantation that were grown for varying periods of time (16, 23, 31, and 53 years) near Zhongfeng in the Mingshan district in the hilly region of western Sichuan, China. Soil samples were collected from the 0–20 and 20–40 cm depth intervals. Six aggregate fractions (>5, 5–2, 2–1, 1–0.5, 0.5–0.25, and <0.25 mm) were obtained by shaking and wet-sieving. In all studied tea plantations, the soil aggregates were dominated by the >5 and <0.25 mm fractions, which were the main pools of C and N. The mean weight diameter (MWD) of soil aggregates in the 23-year-old tea plantation was the greatest, indicating that aggregates in the 23-year-old tea plantation were more stable than in the other plantations. Aggregate stability was more strongly correlated with labile C than with organic C concentrations. Soil aggregates with different particle sizes had considerable variations in their organic C and total N concentrations in all tea plantations. The fractions that were most important to the retention of organic C and total N were the coarse aggregate fractions (>2 mm). The greater C/N ratio of the coarse aggregate fractions implied that their organic C was younger and more labile than that in the fine aggregate fractions (<0.5 mm). Long-term tea cultivation was favorable to the sequestration of soil C and N, especially in the <0.25 mm fraction. However, the rates of C and N sequestration in the whole soil decreased with tea plantation age. It can be concluded that the development and implementation of a suitable management protocol is critically important to the maintenance of soil C and N sinks after 53 years of tea cultivation. [ABSTRACT FROM AUTHOR]

Understanding plant phosphorus (P) assimilation and its root morphological responses is important to acquire an ideal material for remediation of P-enriched environments. Pot experiments were conducted to explore P accumulation and root morphological traits in a mining ecotype (ME) and non-mining ecotype (NME) of Polygonum hydropiper under different organic P (Po) sources (G1P, AMP, ATP, IHP) and inorganic P (Pi) source (KH2PO4), and also their responses to a high level of IHP for different growth periods. Both ecotypes showed higher biomass in Pi and IHP treatments than other Po sources. P accumulation in seedlings were in the order of Pi > IHP > other Po media. Extending the growth period increased biomass and P accumulation in both ecotypes. The ME demonstrated 1.11-1.46 times higher P accumulation than the NME. Seedlings fed with IHP demonstrated significantly greater morphological parameters of fine, medium, and thick roots compared to other Po sources. Total root length, surface area, and volume of both ecotypes significantly increased with the prolonged growth period. The ME has a higher ability to develop root system and exhibits better distribution of fine roots to enhance P accumulation from high P media, and thus it is a worthy material for P-phytoextraction. [ABSTRACT FROM AUTHOR]

Purpose: Establishing tea plantations (Camellia sinensis L.) can markedly change the pools of soil inorganic phosphorus (P) especially in water-stable aggregates. However, the effects of different chronosequence phases on the quantity and quality of inorganic P fractions in such plantations are poorly understood.Materials and methods: This study investigated the inorganic P fractions including the Al bound-P (Al-P), Fe bound-P (Fe-P), occluded-P (O-P), and Ca bound-P (Ca-P) in water-stable aggregates (WSAs) of soil from tea plantations converted from farmland. The investigations included 2–3 (CT2-3), 9–10 (CT9-10), and 16–17 years (CT16-17) and one abandoned land as contrast (CK), which is close to the three different-aged sites of soil from tea plantations converted from farmland in Zhongfeng Township of Mingshan County, Sichuan, southwest China.Results and discussion: The dominant size fraction was the aggregate with 0.5–0.25 mm. Content of > 1 mm fraction gradually increased with the increasing age in tea plantations. The contribution rate is closely related to the content of WSAs. The highest content of Al-P was observed in the aggregate with < 1 mm, Fe-P and Ca-P mainly existed in the aggregate with > 2 mm, and the distribution of O-P was uniform in soil from tea plantations converted from farmland at 0–20 and 20–40 cm soil depths, indicating that aggregate size fractions can influence the concentration of P in different P fractions. The contents of Al-P and Fe-P increased with the increasing age in tea plantations, whereas the contents of O-P and Ca-P decreased in CT16-17.Conclusions: The results of this study show that the distribution of inorganic P fractions can be influenced by aggregate size and inorganic P fractions which had low activity and are transformed into highly available fractions with the increasing age in tea plantations. [ABSTRACT FROM AUTHOR]

Aim: This study focused on P acquisition mechanisms of Hordeum spontaneum from P-impoverished soil by measuring plant growth, P acquisition and rhizosphere properties.Methods: Two P-efficient genotypes (IS-22-30 and IS-22-25) and a P-inefficient genotype (IS-07-07) were subjected to a P supply of 0, 30 mg kg−1 (deficient P) and 60 mg kg−1 (sufficient P) in a rhizobag experiment. After 60 days, biomass, P concentration, and P uptake were analyzed. Changes in pH, P fractions and acid phosphatase activity in soil at different distances from the roots were determined, using a slicing technique.Results: P-efficient genotypes showed greater biomass and plant P content, but lower plant P concentration than the P-inefficient genotype. The average seed P content was 113 and 176 μg P per seed of P-efficient genotypes and P-inefficient genotype, respectively. P-efficient genotypes showed P uptake of 3.0 and 7.9 mg pot−1 at 0 and 30 mg P kg−1; while that of P-inefficient genotype was 1.0 and 5.3 mg pot−1, respectively. Acid phosphatase activity was significantly enhanced in the soil-root interface and P-efficient genotypes demonstrated 54% greater activity of rhizosphere acid phosphatase than the P-inefficient genotype. Rhizosphere P fractions showed that P utilized by the two genotypes mainly came from H2O-Pi, NaHCO3-Pi, and NaOH-Pi, while the P-efficient genotypes markedly depleted NaHCO3-Po, NaOH-Po and HCl-Pi, and the depletion zone extended to 4 mm under P deficiency.Conclusions: These results indicate the potential to sustain more growth and greater P acquisition by P-efficient genotypes of wild barley from P-deficient soil through changes of rhizosphere P fractions and enhancing rhizosphere acid phosphatase activity. [ABSTRACT FROM AUTHOR]